The Gordon Research Conference on "Oxygen Radicals in Biology" is designed to provide environmental toxicologists, biologists, biochemists, cell biologists, clinicians, and other biomedical scientists with state of the art knowledge on reactive oxygen species and their interactions with other radicals, including nitric oxide, in the biological responses to environmental toxicants and the etiology of chronic diseases. This research conference is held every two years; the next meeting will be held February 8-13, 2004 at the Ventura Beach Marriot Hotel, Ventura, California. Twelve conferences have been held since 1981 and they have proven to be extremely productive based on the large number of applicants and the post-meeting evaluations. Funds are requested to partially support travel subsistence and registration costs for speakers from the United States and productive graduate students/post-doctoral candidates. The speakers listed in this program were selected based on the suggestions from the previous chairs, co-chairs and attendees at the past conference. Speakers have been invited to present their latest research on oxygen radicals in biology. Topics to be covered include: mechanisms of action of antioxidants; mechanism and consequences of protein oxidation; the regulation of thiol redox state and cellular function; the redox cell signaling in the context of environmental exposure to toxins; and cardiovascular and neurodegenerative diseases. In addition, Professor Bruce Freeman will present a Plenary Lecture entitled: "From Xanthine Oxidase to Nitric Oxide; Radicals in Circulation." Two separate poster sessions of two days each are scheduled for an anticipated 50-70 posters. Total attendance is limited to 135 by Gordon Conference rules. The Gordon Conference provides an excellent and much needed forum for the diversity of both participants and research areas. The main strength of this Gordon Research Conference is the opportunities offered for scientists in different disciplines to interact in an extended and uninterrupted fashion. This type of interaction generally results in new collaborative research initiatives. The Gordon Research Conference on Oxygen Radicals in Biology plays a crucial role in exploring frontier research in this important field relevant to understanding of the molecular events that occur on environmental exposure and chronic disease.